A new survey released Wednesday paints a bleak 2010 picture for Kentucky Sen. Jim Bunning (R), who was already considered the most vulnerable Senate incumbent up for re-election.

The automated survey by the Democratic firm Public Policy Polling gave the embattled Senator a 28 percent job approval rating with 54 percent disapproving. Only 38 percent of those surveyed held a favorable opinion of Bunning.

Meanwhile, four prospective Democratic challengers — who are either running or have been mentioned as possible candidates in the race — beat Bunning in hypothetical matchups.

Of all the possible Democratic candidates, Rep. Ben Chandler (D) performed the best in the PPP poll, leading Bunning by 14 points. Meanwhile Kentucky Attorney General Jack Conway, who is widely expected to throw his hat into the contest, held a 9-point edge over Bunning, while state Auditor Crit Luallen was up 8 points over the Senator.

Lt. Gov. Dan Mongiardo (D) — who lost to Bunning by just 2 points in 2004 and announced in January that he plans to run again in 2010 — held a 7-point lead in a hypothetical matchup.

The survey of 610 Kentucky voters was conducted April 2-3 and had a 4 percentage point margin of error.

With dismal poll numbers and fundraising that Bunning himself has described as “lousy,— some Bluegrass State and national Republicans are hoping he will step aside and let another GOP candidate run.

Secretary of State Trey Grayson (R), who has said he would consider a bid if Bunning retired, would certainly begin the race in a better position. Grayson is viewed positively by 46 percent of voters, with 19 percent holding an unfavorable opinion.

Grayson fared better than Bunning in a hypothetical matchup, but still trailed Chandler by 6 percentage points and Conway by 4 points. Grayson lead Luallen by 2 percentage points and Mongiardo by 4 points.

Meanwhile, state Sen. David Williams (R), who has met with the National Republican Senatorial Committee about a possible run this cycle, had a 28 percent favorable and 41 percent unfavorable rating. He also lost prospective matchups against Chandler, Conway, Luallen and Mongiardo by double-digit margins.